Electrically operated visual indicator



March 1953 M. M. BROOKES ET AL 2,632,888

ELECTRICALLY OPERATED VISUAL INDICATOR Filed NOV. 13, 1950 .1 4 Stops fi l 23 Stops /7 Pole Piece F25 l6 1/ ,/23 I I4 /8 Pole Piece /9 1 I5 I fil ,lll ,d h ZOPermanent ML j y 2724 Magnet 20 Permahent Magnq/ I A. 10 515%.

v '77l;;n230f5:- 2 2M 5 {7 @QWQMI Attorneys.

Patented Mar. 24, 1953 UNITED STATES @ATENT OFFICE...

ELEQTRIIGALLY OPERATED VISUAL INDICATOR Application November 13, 195.0,.Seria1No. 185,437 In Great Britain October 13; 1949 9 Claims.

The presentinvention relates-to indicating mechanisms, and more particularly relates to electrically operated indicators of" the kind adapted to give at least a visual indication.

Such indicators are commonly used for-example, as calling indicators in manually operated telephone exchanges. in conventional form these calling indicatorsconsist of; an electromagnet co-operating with a pivoted armature which spring loaded to keepitremote from the electromagnet pole piece when the electromagnet is not energised, and an indicating flag or shutter mechanically linked to the armature to give a visual indication when the armature is attracted. to the pole piece.

One object of the present invention is to pro vide a novel construction of indicator which may be more simple than the above mentioned conventional' form.

According to the present inventionthere is provided' an indicator of the kind specified comprising an electromagnet having a pair of'pole pieces, and a permanently magnetised member. arranged for rotation betweensaid'pair of polepieceswitm out contact therewith, the arrangement being such that energisation of said electromagnet causes said member to rotate through a predetermined angle and thereby providethe required indication.

The. arrangement may be such thatthe memher is self-restoring to a non-indicating position when the electromagnet is (lo-energised, or, it may be restored manually or, by reversing the current through the electromagnet winding.

One embodimentof the present invention will now be described, by way of example, as applied to an indicator adapted for use as atelephone calling indicator, the embodiment beingdescribed with reference to the .accompanying,drawings, in which:.

Figure 1 is a plan View of the indicatoirwith part of the electromagnet sheath shown broken away,

Figure 2 is a side view of the indicator in the non-operative condition with one side bracket which supports the cylindrical magnet removed for clarity, whilst Figure 3 is a part view similar to Figure 2 showing the cylindrical magnet in its operative position, and

Figure 4 is an end view'of the front of the indicator.

Referring now to the drawings it will be seen that in this embodiment the indicator comprises a soft iron sheath Ill of square cross section, open at each end, inwhich ishouseda soft ironcore. H provided with anenergising winding l2; Asoft iron piece 13' is provided at one end of thezsheath ID. to complete a magnetic .patlr'between the'core I Land the sheath 10.. Joined to the soft iron piece I3 is a sheet orlnsulating-material Mcarrying four contact pins it to 'two'of 'which' are connected leads from the winding l2: A't-the-other end the-core li projects through aninsulating. end plate to and has a pole piece' ll 'i'n the'form of a plate of curved'cross-section attached thereto; One side of the sheathiil at this-latter-end'is extended with the first: portion of the extended side in the same plane as the remainderofthe side, and the other; portion bent to'form' a" second pole piece id of similar shape toth'e' flrstpole piece but provided'with-a rectangular-aperture f9 therein. The arrangement is such-thatthe pole pieces ii and it effectively partially enclose a cylinder, with two air gaps between the pole pieces. A circular cylindrical permanent magnet 2c is supported'in the space between *thepol pieces I? and it by pivots 2'! mountedinthe side arms of a bracket of non-magneticmaterial which is secured to the fiat: portion of the extended side. The mounting of the magnet cylinder 20. andthe shape of the pole pieces l7 and i8 issuchthat the air gap therebetween' is not uniform; The air gap between the pole piece i8 and the magnet cylinder 26 decreases, from the free end of the pole piece It towards the centre whilst the air gap between the pole piece IT and the magnet cylinder it decreases. from that end of the pole piece ll adjacentthe extended side of the sheath it in a similar manner. At one side of the magnet cylinder 26 a cam member22'is fitted onthepivot 2 l and-is adapted to co-operate with stem 23" and 24 to limit the extent of rotation of the mag= net 26. Themagnetflt is magnetised transversely to its axis of rotation and is arranged so that with the cam member 22 resting on thebackstopi 23, the magnetic axis, indicated by the broken lineEB approximately bisectsthe longitudinal axis of the cam member22. The cammember 22 co-operates with a pair of off-normal contacts 26 fitted'on the insulating plate 5%, the contacts 25 being closed'by the cam member 22 when the magnetZG" is rotated so that the cam}! is resting on the front stop 24.

The operation of the indicator-"is -as-foilowsz With the ele'ctromagnet winding I [not energised thelocation and dimensions'of the radial'air gaps between the pole pieces IT and I8" are such" that the magnet 2t. rests with the cam 22 on the back stop 23. When the electromagnet winding JT'is energised by direct current. in the correct. direction, however, they resulting magnetic field .be.-.

tween the pole pieces-ll and, it causes, themag net 263 to rotate in order to move the magnet poles nearer to the pole pieces Mend it, which brings the cam 22 to rest on the front. stop 24- The shape of the air gaps-between the. magnet-.

cylinder 20 and the pole; pieces-Hand. I8 :is

designed ,to. give a progressively ;decreasin '-e.-; luctance; and consequently, increasing. magnetid attraction at this point, so that the magnet cylinder 20 is accelerated during its movement from the back stop 23. Similarly on the de-energisation the magnet cylinder 20 is accelerated in the course of its restoring movement. When the winding I2 is de-energised the magnet 26 is self restoring to its original position. The magnet 20 is suitably marked, for example with white paint, on the part of the periphery which can be seen through the aperture I9 in the pole piece I8 when the cam 22 rests on the front stop 24, so that this movement of the magnet 20 provides the required indication by virtue of the appearance of the marking in the aperture I9. At the same time the oiT-normal contacts 26 are made, and these can be used to complete the circuit of any known form of audible indicator for use, for example, as a night alarm.

In use a dust cover of non-ferrous material will be fitted over the pole piece end of the indicator and will overlap the adjacent end of the soft iron sheath. A transparent window will be provided in the end of this cover corresponding to the aperture in the pole piece.

The above described arrangement can be modified slightly where it is desired that the indicator shall not be self restoring. In this modified arrangement the magnet 20 is arranged so that when moving between the back stop 23 and the front stop 24 its magnetic axis passes through the position of maximum reluctance as determined by the shape of the pole pieces. This results in the magnet being in a rest position on either stop so that the indicator remains in the operated position after the electromagnet winding has been de-energised. A simple spring controlled element of conventional type can be used for manual restoration; alternatively the current through the electromagnet winding may be reversed.

. Indicators according to the present invention have the advantages over a conventional indicator of the above described form that the magnet which is the usual armature can also function as the indicator, no separate indicating flag with mechanical linkage thereto being necessary. Generally no restoring spring is necessary, although in some modifications a simple element may be used. Thus a simplified construction is possible with resultant ease of assembly and maintenance.

What we claim is:

1. An electrically operated visual indicator comprising an electromagnet having a pair of confronting pole pieces, and a rotatable permanently magnetized member arranged for angular movement between said pair of pole pieces upon energization of said electromagnet, said magnetized member having a part of its periphery distinctively marked whereby a required indication is provided by said magnetized member upon angular movement thereof.

2. An electrically operated visual indicator as recited in claim 1, wherein said pole pieces are of curved cross-section as viewed in a plane transverse to the axis of angular movement of said magnetizedmember, each pole piece being spaced from the adjacent portion of said magnetized member by an air gap which decreases in radial length from one end of the pole piece circumferentially towards the other end thereof, and the narrow end of each air gap being adjacent the broader end of the other air gap.

3. An electrically operated visual signal indicator as recited in claim 1, in combination with a pair of electrical contacts, and a member secured to said permanently magnetized member and cooperating with said electrical contacts to cause a change of state of operation thereof upon angular movement of said permanently magnetized member.

4. An electrically operated visual indicator comprising an electromagnet having a pair of op posed pole pieces of curved cross section arranged to partially enclose a cylindrical space whilst leaving two air gaps between the pole pieces, a cylindrical permanently magnetised member rotatably supported between said pole pieces for rotation upon energisation of said electromagnet, and stop means limiting the angular rotation of said magnetized member, said magnetized member having a distinctive marking on its periphery, which marking provides the required visual indication upon rotation of said magnetized member.

5. An indicator according to claim 4, in which a pair of electrical contacts are provided, and a member secured to said permanently magnetized member cooperates with said electrical contacts to cause a change of state of operation thereof upon rotation of said permanently magnetized member.

6. An electrically operated visual indicator comprising an electromagnet, said electromagnet having an energising winding surrounding a central soft iron core and a soft iron sheath enclosing said winding, a pole piece joined to said core and a further pole piece joined to the adjacent end of said sheath, said pole pieces being of curved cross-section and partially enclosing a cylindrical space whilst leaving two air gaps be tween the pole pieces, and a cylindrical permanently magnetised member rotatably mounted between said pole pieces.

7. An indicator according to claim 6, in which the pole piece joined to the sheath has an aperture therein through which a portion of the periphery of said permanently magnetised member is visible.

8. An indicator according to claim 6, in which the air gap between each pole piece and the adjacent portion of said permanently magnetised member decreases from one side of the pole piece to the other.

9. An electrically operated telephone indicator comprising an electromagnet having a pair of arcuate pole pieces, one of said pole pieces having an aperture therein, a cylindrical permanently magnetized rotor, said cylindrical rotor being supported in brackets between said pole pieces, and stop means limiting the movement of said rotor on energisation of said electromagnet, said rotor having a portion of its periphery distinctively marked, said portion being visible through said aperture only in the position of said rotor to which it rotates on energisation of said electromagnet.

MAURICE M. BROOKE'S. FREDERICK E. ROMMEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,913,937 Loefiler June 13, 1933 2,245,493 Nothe June 10, 1941 2,367,299 McLarn et al Jan. 16, 1945 2,405,429 Jewell Aug. 6, 1946 2,415,452 Taylor et a1 Feb. 11, 1947 

